Solenoid Valve

ABSTRACT

A solenoid valve for controlling a fluid has a first housing part ( 2 ), an axial guide ( 3 ), facing inwards, for an armature ( 4 ) which can be displaced in the axial guide ( 3 ) under the effect of a solenoid ( 5 ) that at least partially surrounds the exterior of the first housing part ( 2 ), a return spring ( 6 ) and a closing element ( 27 ) impacting a valve closing element ( 7 ), and a second housing part ( 9 ) which is arranged coaxially to the first housing part ( 2 ). The solenoid valve according to the invention is characterized in that the first housing part ( 2 ) has a reduced wall portion ( 17 ) which faces inwards towards the armature ( 4 ) and the second housing part ( 9 ) and which effects a magnetic separation of the two housing parts ( 2, 9 ) to at least some extent.

REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.13/261,220 filed Mar. 16, 2012, the entire subject matter of which isincorporated herewith by reference.

FIELD OF THE INVENTION

The invention relates to a solenoid valve for controlling a fluid havinga first housing part, with an axial guide which is oriented toward theinterior for an armature which, under the action of a solenoid that atleast partially surrounds the first housing part to the outside, can bemoved in the axial guide, with a reset spring and a closing elementwhich acts on the valve closing member, and having a second housing partwhich is located coaxially to the first housing part.

BACKGROUND OF THE INVENTION

DE-U-85 22 724 describes a solenoid valve with a first cylindricalhousing part formed from a ferromagnetic material and a second,sleeve-shaped housing part which likewise consists of a ferromagneticmaterial for accommodating a magnet armature which controls a valve seatbody of the valve. For this purpose, the valve seat body has severalhydraulic medium ports which, in the base position of the solenoidvalve, are hydraulically separated from one another by a plunger whichis attached to the magnet armature. The two housing parts themselves aremagnetically separated from one another, but are physically connected bya ring-shaped, further housing part made of a nonmagnetic material inthis respect. The indicated magnetic separation by way of the furtherhousing part serves among other things to oppose a so-called magneticshort circuit in any case and to ensure effective feed of the magneticlines of force into the magnetic armature if the actuating coil of theknown solution is energized.

Due to the further housing part consisting of a nonmagnetic material,the known solution is, however, relatively expensive to implement formagnetic separation and it has been shown that, especially when theknown solenoid valve is used at high pressures, a failure site is formedby the other ring-shaped housing part for the magnetic separation.

In order to correct these disadvantages, DE 100 38 139 B4 has alreadyproposed in a guide element of a magnetizable base material and at leastone region of reduced magnetizability that the region of reducedmagnetizability be implemented as a kind of integral component of thebase material. In one configuration of the known teaching, acircumferential groove is made in a pressure pipe suitable for solenoidvalves and is provided with an additive material of reducedmagnetizability by means of a laser application method or laser weldingmethod, where austenitic materials are indicated as especially suitable,such as in particular nickel, chromium, and manganese, but these lasertreatment methods are also associated with a certain cost.

EP 0 951 412 B2 discloses a generic solenoid valve for the actuation ofliquid and gaseous working media, this solenoid valve being usableespecially for hydraulic brake systems for motor vehicles. The knownsolenoid valve has a first, preferably cylindrical housing part which issurrounded by a solenoid and which forms a receiver for an armature. Thereceiver forms an axial guide for the indicated armature, and an energystorage mechanism in the form of a reset spring acts on the armaturetogether with a valve stem which acts on it and which, designed as akind of valve closing member, for a closing solenoid valve presses on avalve seat that interacts with corresponding fluid ports within thevalve body. Coaxially to the first housing part, there is a secondhousing part which has a cylindrical recess that runs in thelongitudinal extension of the solenoid valve and that is connected tothe indicated valve ports and is located in the valve seat.

The first and the second housing part are produced in one piece from aferromagnetic material which surrounds the armature in the form of athin-walled sleeve which serves as a pole tube and whose wall thickness,which remains the same over its length for reducing a magnetic shortcircuit, should be no greater than is necessary for reliableaccommodation of the mechanical stress. The integral execution of thefirst with the second housing part, which is necessary in this respect,is done preferably via metal cutting steps and can presupposecorrespondingly high production and mounting accuracies.

SUMMARY OF THE INVENTION

Based on the aforementioned prior art, the object of the invention is tomake available to the experts in the field a solenoid valve which issimple to produce and mount and which moreover ensures reliable,effective magnetic separation to prevent short circuits. This object isachieved by a solenoid valve where the first housing part is providedwith a wall reduction which is oriented toward the interior in thedirection of the armature and of the second housing part and which atleast partially effects a magnetic separation of the two housing partsfrom one another. The indicated wall reduction can be easily obtainedusing production technology, for example, using a rolling treatment toolor pressing tool, and in particular the solution according to theinvention does not require the introduction of additive materials inorder to help prevent a magnetic short circuit and to be able to effectmagnetic separation in order to increase the efficiency of the magneticsystem. As a result of the depression which is made from the interiorand which forms the wall reduction of the first housing part, thematerial of the wall of the housing is compressed in this respect sothat even at higher compressive stresses, reliable steadying by theindicated wall compression is achieved. Alternatively, the depressioncan also be made by cutting so that there is no compression of thematerial in this region. If, for the purposes of this invention,therefore reference is made to a wall reduction, this expresses the factthat viewed geometrically, there is a recess on the inside of the wallof the housing part; but no weakening of the material in terms of a lackof compressive stiffness need be assumed. For one with average skill inthe art in the field of solenoid valve technology, it is surprising thathe achieves reliable magnetic separation with a wall reduction and stillproduces effective compressive steadying by the compression of theremaining wall thickness material so that even in the event of failureof the solenoid valve, high pressures can still be reliably accommodatedby parts of the magnetic housing relative to the fluid flow or flow ofmedia.

The first housing part is preferably formed in the manner of athin-walled sleeve as a pole tube in the region of the axial guide forthe (magnet) armature, with the sleeve moreover projecting into orbeyond the second housing part. Because the first housing part in theoverlapping region with the second housing part is constituted as athin-walled sleeve, the first housing part can be fixed on the secondhousing part by a forming process, such as, for example, by flanging,without the already mentioned compressive stiffness of the overalldevice being adversely affected in the process.

Advantageously, it is provided that there be a groove around the outercircumference on the second housing part and that the edge of the firsthousing part be crimped into it. In addition to a compressively verystrong connection of the first housing part to the second housing part,a sealing contact connection is also created in this way.

An especially reliable arrangement for the solenoid valve according tothe invention is achieved if the indicated wall reduction is provided inan overlapping region of the armature with the second housing part, inwhich a ring-shaped end of the armature overlaps a step-shaped shoulderon a side of the second housing part that is adjacent to the armature,where especially preferably, in a position spaced away from the armatureto the housing part, a middle section of the groove in the sleeveoverlaps an empty space in the overlapping region so that in this way,in addition to a magnetic decoupling, a reliable, power-guidingintroduction of the magnetic lines of force into the armature can takeplace with the valve actuating part.

The individual components of the solenoid valve can also be more easilymounted owing to the simplified handling of two housing parts which arekept shorter in their axial length.

In one structurally advantageous version of the solenoid valve, in theregion where the groove is located, the armature is formed as s cylinderwhich in a traveling motion partially crosses the second housing partwhich is formed as a piston in this region, and thus, regardless of itsposition, is continuously in centered engagement with the first housingpart.

One option of manually opening the solenoid valve in a kind of emergencyoperation for a malfunction, for example, dictated by a failure of thesolenoid, is enabled by a rod-like stem being supported in the secondhousing part to be axially displaceable and it being able to be actuatedfrom the outside by means of a set screw which is guided to be able toturn in the second housing part. The extension itself is provided with aradial widening on its one free end and in this way is secured to beaxially immovable in the indicated set screw. However, when the setscrew or actuating screw is turned by hand, the stem can move thearmature, and in this respect the tip, which is connected to thearmature as a closing element, is lifted by the valve closing member.The closing element with its tip is inserted into the armature on itsfree end side and is held by means of a steel ring and a flange. Evenfor a tight armature, releasing the valve closing member is thus easilypossible as soon as the rod-shaped stem with its widened end takes holdof the armature after an idle stroke. In the armature, the closingelement itself can have a certain radial play so that even in the eventthat there are production-dictated alignment errors, the cone of theclosing element with its free tip strikes the pilot seat on the valveclosing member in the middle without difficulty.

In the valve member, a kind of nonreturn valve is preferably installedwhich, together with the tip of the closing element, clears or closes abypass bore in the valve closing member. The reset spring or anothertype of energy storage mechanism is preferably to be located in a recessin the armature around the stem. The assignment of the valve ports andthe shape of the valve closing member can be configured such that flowthrough the solenoid valve in both directions is possible. The resetspring can be supported on the armature and the second housing partpreferably to bring about a closed position of the valve closing member.

BRIEF DESCRIPTION OF THE DRAWING

The invention is detailed below using one exemplary embodiment which isshown in the drawing. The single FIGURE shows a schematic longitudinalsection through the solenoid valve according to the invention, not toscale.

DETAILED DESCRIPTION OF THE INVENTION

The FIGURE shows in a longitudinal section a solenoid valve 1 forcontrolling a fluid, such as a liquid working medium for a hydraulicconsumer of a hydraulic system, which consumer is not detailed. Thesolenoid valve 1 is made as a piloted valve which can be activatedelectromagnetically. In its essential parts, the solenoid valve 1consists of a cylindrical first housing part 2 with dimensions thatchange incrementally along its outer and inner diameter.

With its connecting branch 32, which is shown on the right edge in FIG.1 with an O-ring 34 which has been inserted into a circumferentialgroove 33, the first housing part 2, forms a fluidic connection to ahydraulic system, not shown, especially to a hydraulic consumer. Theconnecting branch 32 is part of a valve body 35 in whose axial regionthe first housing part 2 has a large wall thickness compared to itsother wall regions. In this respect, the connecting branch 32 forms atype of cartridge valve. A valve port 29 which is made radially in thevalve body 35 from the two sides can be connected to its valve port 30,which is routed centrally and axially out of the connecting branch 32,where a valve closing member 7 made as a valve spool controls thisfluid-carrying connection. The valve closing member 7 is made as astepped spool and is axially actuated by way of a closing element withtip 27. The press fit 24 is created by a sealing means 25 in the mannerof an O-ring fitting into corresponding receivers resting on the closingelement and on the armature 4. The valve closing member 7, with itsright edge shown in FIG. 1, forms a valve seat together with the borewhich constitutes the valve port 30.

The conical closing element with its tip 27 rests in a bypass bore 28 inthe valve closing member 7 with its right free end. A second bypass bore28′, which extends through the valve closing member 7 radially with adistance to the bypass bore 28 which projects centrally through thevalve closing member 7 and is arranged parallel to the latter, isconnected to the valve port 29 to carry fluid via a correspondingthrottle site Likewise, the bypass bore 28 is connected via a throttlesite to a rear pressure space 36, where the tip of the closing elementin the operating position shown in the FIGURE mates with this throttlesite. In this respect therefore, the bypass bore 28′, with the tip 27 ofthe closing element removed, forms a fluid-carrying connection withrespect to the rear pressure space 36, which extends between magnetarmature 4 and the facing end side of the valve closing member 7.

A nonreturn valve 26 is located on the end of the valve closing member 7facing the valve port 30. Viewed in the direction of looking at theFIGURE, on the left the first housing part 2 undergoes transition fromthe valve body 35 into a thin-walled sleeve 14, which forms theso-called pole tube within the solenoid valve. Furthermore, the sleeve14 forms an axial guide 3 for the armature 4 over a length whichcorresponds to about half its total length. A lubricating medium can beplaced between the magnet armature 4 and the sleeve 14, or parts of theinner housing wall of the sleeve 14 are widened in their outsidediameters relative to the other wall parts somewhat in diameter so thatoffset lubricating pockets form in which the fluid then forms a kind ofsliding seal for the magnet armature 4.

The rod-shaped stem 8 extends through the piston-like armature 4, whichcan move depending on the energizing of a solenoid 5 surrounding thesleeve 14 in its essential length. The stem 8 is guided with anextension 11 through a recess 10 of a second housing part 9 whose freeend region is adjoined by a set screw 23 which is rotationally guided byway of a corresponding inner screw connection in the second housing part9. When a head 37 with a knurl is turned, the stem 8 can be moved andcan clear the valve closing member 7 via the armature 4 and the closingelement which has been inserted into the armature 4 with tip 27 in thesense of an opening position. External cover caps can be removed fromthe other magnet housing parts for the corresponding emergencyoperation.

Like the first housing part 2, the second housing part 9 is essentiallya cylindrical, one-piece body, with corresponding diameter adjustmentsalong its outer side. The second housing part 9 is surrounded by thesleeve 14 of the first housing part 2 to approximately to half of theaxial extension, forming a plug connection 12, with the second housingpart 9 having a circumferential groove 16 into which an edge 15 of thesleeve 14 is crimped. The forming region 13 of the sleeve 14 in thelongitudinal section is constituted as right-angle bend; i.e., afterforming, the edge 15 comes to rest offset in parallel in thecircumferential groove 16. This molding process can be carried out witha pressing tool or rolling treatment tool. Furthermore, there is anO-ring 38 between the sleeve 14 and the second housing part 9 in agroove of the second housing part 9, and thus it seals the first housingpart 2 against the second housing part 9.

For magnetic separation of the two housing parts 2, 9, in the axialmiddle of the solenoid 5, the sleeve 14 is provided with a wallreduction 17 to approximately half of the other wall thickness of thesleeve 14. The wall reduction 17 is formed by a groove 18 with flanks 20which extend flat on the inner circumference 19 of the sleeve 14.Furthermore, the wall reduction 17 encompasses the inner region of thesleeve 14 in the manner of a ring. The wall reduction 17 facilitates themagnetic separation, especially between the two housing parts 2, 9, andthe armature 4 is located in its forward position shown in the FIGURE,between an annular end 39 of the armature 4 and an adjacent, assignedstep-shaped shoulder, on a side of the second housing part 9 adjacent tothe armature 4, an empty space is formed which further promotes themagnetic separation on the one hand and on the other hand allows adefined transition of the lines of force from the armature 4 to thehousing part 9. Moreover, with this type of production of the magneticseparation of the two housing parts 2, 9 from one another, no thermalloading of the components is necessary at all, such as, for example, inthe known hard-facing of a nonmagnetic material, so that, when thecomponents are joined, stresses and material distortion that adverselyaffect the accuracy cannot occur. The indicated empty space can also befilled with fluid, which can be accordingly displaced again in thetravelling motion of the armature 4, for example, via the sliding sealof the armature 4.

There is a small radial play of the armature 4 in the region of the wallreduction 17. In all other respects, the armature 4 with its ring-likeends is guided in the second housing part 9. In this way, in theoverlapping region 21 a type of piston-cylinder arrangement isimplemented which acts on the armature 4 to center it so that it isalways supported in a guided manner on the second housing part 9 at itsleft and right free ends.

As an energy storage mechanism, a reset spring 6 is placed around thestem 8 in a cylindrical bore of the recess 22 which extends from the end39 of the armature 4 that faces the second housing part 9. The resetspring 6 is supported on a seal arrangement 40 around the stem extension11. The seal arrangement 40 is placed around the extension 11 in themanner of a gland packing and seals the stem 8 in turn to prevent lossof a hydraulic medium relative to the second housing part 9. In theintermediate space between the armature 4 and the second housing part 9,hydraulic media can appear which, via a longitudinal bore 42 in thearmature, can traverse the latter from its rear end side to the frontend side in the direction of the pressure space 36 and vice versa. Inthis way, there is balancing of the hydraulic medium so that in theregion of the armature 4 neither an overpressure nor an underpressurecan build up which could otherwise lead to problems in the operation ofthe armature 4. The solenoid valve 1 furthermore has a shieldinghousing, especially around its solenoid 5, with appropriate plastic andelastomer material being used here. This magnet structure isconventional for solenoid valves so that it will not be further detailedhere. To energize the solenoid 5, a plug 41 is used which is attached tothe upper side wall of the valve housing for linking to a control andcurrent supply unit, which is not detailed.

Flow can take place through the valve body 35 of the solenoid valve 1both from the valve port 29 to the valve port 30 and also vice versa. Inthe energized state of the solenoid 5, the armature 4 and the closingelement with tip 27, as well as the valve closing member 7, viewed inthe direction of looking at the FIGURE, are moved to the left againstthe reset force of the reset spring 6, with flow through the valve body35 in both directions between the valve ports 29 and 30 then beingpossible.

In the unenergized state of the solenoid valve, however, flow of thehydraulic medium from the valve port 29 to the valve port 30 isprevented; but conversely there is the possibility that the fluidconnection may exist between the valve port 30 and the valve port 29.For this flow direction from port 30 to port 29, however, the valvespool 7 must be pushed against the force of the reset spring 6; thistakes place, for example, at a pressure difference of about 1.5 bar(check function). As described, the solenoid 5 is not energized here.With the solution according to the invention, a type of 2/2-way seatvalve is therefore implemented which, magnetically actuated and pilotedas a cartridge valve, can control pressures of even 350 bar and which isclosed in the normal state and which, as shown, allows a return orreverse flow function.

What is claimed is:
 1. A solenoid valve for controlling a fluid having afirst housing part (2), with an axial guide (3) which is oriented towardthe interior for an armature (4) which, under the action of a solenoid(5) that at least partially surrounds the first housing part (2) to theoutside, can be moved in the axial guide (3), with a reset spring (6)and a closing element (27) which acts on the valve closing member (7),and having a second housing part (9) which is located coaxially to thefirst housing part (2), characterized in that the first housing part (2)has a wall reduction (17) which is oriented toward the interior in thedirection of the armature (4) and of the second housing part (9) andwhich at least partially effects magnetic separation of the two housingparts (2, 9) from one another.
 2. The solenoid valve according to claim1, characterized in that the first housing part (2) has a thin-walledsleeve (14) as a pole tube which essentially forms the axial guide (3)for the armature (4), and that the second housing part (9) projects intothe sleeve (14) at least partially in contact with the sleeve (14). 3.The solenoid valve according to claim 2, characterized in that thesleeve (14) has the wall reduction (17) in the form of a groove (18) onits inner circumference (19).
 4. The solenoid valve according to claim3, characterized in that the groove (18) has flat flanks (10) whichextend to the adjacent wall regions of the sleeve (14).
 5. The solenoidvalve according to claim 1, characterized in that the wall reduction(17) is located in an overlapping region (21) of the armature (4) withthe second housing part (9), in which a ring-shaped end (39) of thearmature (4) overlaps a step-shaped shoulder on a side of the secondhousing part (9) that is adjacent to the armature (4).
 6. The solenoidvalve according to claim 5, characterized in that in a position spacedaway from the armature (4) to the housing part (9), a middle section ofthe groove (18) in the sleeve (14) overlaps an empty space in theoverlapping region (21).
 7. The solenoid valve according to claim 1,characterized in that the first housing part (2) and the second housingpart (9) are connected to one another as a plug connection, in which thefirst housing part (2) at least partially overlaps the second housingpart (9) viewed in the axial direction of actuation of the valve, andthat one free end of the housing part (2) made as a flanged edge mateswith a circumferential groove (16) in the second housing part (9). 8.The solenoid valve according to claim 7, characterized in that the otherfree end of the first housing part (2) forms a valve body (35) for thevalve closing member (7), which valve closing member, to the extent thatit is concomitantly controlled by the closing element (27), clears orblocks a fluid-carrying connection between two valve ports (29, 30) ofthe valve body (35).
 9. The solenoid valve according to claim 1,characterized in that the second housing part (9) has a set screw (23)that is dynamically connected to a stem (8), and, when the set screw ismanually actuated, the stem (8), which with an extension (11) at leastpartially extends through the second housing part (9) along an axiallyrouted recess (10), can be moved together with the armature (4) into aposition in the sense of an opening of the valve closing member (7). 10.The solenoid valve according to claim 1, characterized in that thesolenoid valve (1) is piloted.